1. Field of the Invention
This invention relates generally to devices for controlling the hydraulic operating pressure of hydraulic presses as used for laminating plywood.
2. Description of the Prior Art
A common problem with known type hydraulic laminating presses for plywood and the like is that the operator must consult a table in order to determine the amount of hydraulic line pressure for the press in pounds per square inch depending on the panel size (area) and desired unit pressure to be applied to said panel (pounds per square inch). The misuse of this table will result in over-pressure with the resultant plywood panel being too thin with glue being squeezed out or the other extreme of under-pressure being applied with a result in poor bonding.
Another problem with known type controls for plywood hydraulic presses and the like is that when different sizes of plywood panels are being pressed, or different numbers of panels are being pressed, with the numbers varying from time to time, it is often quite easy to make a mistake on the part of the operator with the result of failure to properly control the hydraulic pressure of the press in order to effect the desired resultant panels.
Another problem with controllers for different types of systems employing hydraulic or pneumatic fluid control is that the devices do not accurately combine the several inputs of desired analog quantities in order to produce an overall resultant control which is accurate.
Known prior art U.S. Pat. Nos. which may be pertinent to this invention are as follows: 2,717,421 C. T. Beeson Sept. 13, 1955, 2,726,775, C. W. Howard Dec. 13, 1955, 2,784,754 V. Berthelsen Mar. 12, 1957, 2,810,930 M. D. MacDonald et al Oct. 29, 1957, 3,309,510 I. Brown Mar. 14, 1967, 3,311,837 H. Moreines Mar. 28, 1967, 3,313,984 A. C. Hupp Apr. 11, 1967, 3,331,411 G. Cecchi July 18, 1967, 3,454,787 S. C. Gelernter July 8, 1969, 3,855,101 H. M. Wilson Dec. 17, 1974, 3,873,855 J. N. Reddy Mar. 25, 1975, 3,875,427 R. B. Riley Apr. 1, 1975, 3,879,668 A. P. Edwards Apr. 22, 1975, 3,932,766 D. Kudeljan et al Jan. 13, 1976.
None of these known prior art devices offers the new and unique features of the invention disclosed herein.